Rename autolinking-ios.rb script and bring RNTester and template in line.

[alloy]

Summary

Make the script ready for picking in 0.62.0-rc.3.

• Rename the script to remove ambiguity. “autolinking” is a CLI feature where 3rd-party pods are automatically discovered: https://github.com/react-native-community/cli/blob/master/docs/autolinking.md
• Make the Flipper version of the pods configurable, as requested here.
• Make RNTester’s Podfile use the same form as the template–including enabling Flipper by moving the CPP define into the right place in the Xcode project and out of the Podfile.
• Get rid of Podfile.lock thrashing by making the default CDN spec source explicit.

Changelog

[iOS] [Changed] - Disambiguate autolinking-ios.rb script from CLI’s “autolinking” feature and bring RNTester & template in line.

Test Plan

RNTester builds, as does a new application.

[alloy]

Hmm, I see that I accidentally pushed this to the Facebook remote, my bad. I’ll configure my checkout to default to my fork for next time.

[facebook-github-bot]

@TheSavior is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[elicwhite]

Can you rebase on top of master? I got some merge conflicts when importing. Looks like one of these files may have been changed since

[alloy]

Can’t force push to this branch on the fb repo, so created a new PR from my fork #28077